import java.util.Stack;

class Solution1 {
    public int evalRPN(String[] tokens) {
        Stack<Integer> stack = new Stack<>();
        for(String x : tokens){
            if(!isOperation(x)) {
                stack.push(Integer.parseInt(x));
            }else {
                int num2 = stack.pop();
                int num1 = stack.pop();
                switch (x) {
                    case "+":
                        stack.push(num1+num2);
                        break;
                    case "-":
                        stack.push(num1-num2);
                        break;
                    case "*":
                        stack.push(num1*num2);
                        break;
                    case "/":
                        stack.push(num1/num2);
                        break;
                }
            }
        }
        return stack.pop();
    }
    private boolean isOperation(String x) {
        if (x.equals("+") || x.equals("-") || x.equals("/") || x.equals("*")) {
            return true;
        }
        return false;
    }
}
